Brake disc

ABSTRACT

The invention relates to a brake disc for a disc brake, in particular in motor vehicles. Said brake disc comprises a friction ring ( 12 ) and a pot-shaped supporting part ( 14 ), the friction ring consisting of several ring segments ( 18 ), which adjoin one another in a circumferential direction. To provide a construction that can be commercially produced in a cost-effective manner and that is not prone to warping, the ring segments are provided with semi-circular recesses ( 18   a ), which encompass retaining bolts ( 16 ) that extend radially. The retaining bolts are fixed in circumferential sections of the supporting part and support the ring segments by means of a positive fit in a centrifugal direction. The retaining bolts are preferably configured in a tubular manner.

[0001] The invention relates to a brake disc for disc brakes, especially in motor vehicles, as claimed in the preamble of claim 1.

[0002] Such a brake disc is disclosed for example in DE 33 15 122 A1. Here the brake disc is composed of several ring segments each of which overlap one another in the frontal contact area and are joined to one another by means of a retaining bolt.

[0003] The object of the invention is to develop the generic brake disc such that it is easier to produce and it is lighter especially in the frontal contact area of the ring segments and thus is less sensitive to temperature.

[0004] This object is achieved as claimed for the invention with the characterizing features of claim 1. Advantageous developments of the invention can be learned from the other claims.

[0005] It is proposed as claimed in the invention that each ring segment in the frontal contact area encloses the retaining bolts to the extent of one half in the radial direction, that the retaining bolts are mounted in the circumferential sections of the supporting part, and that the retaining bolts provide positive-locking support for the ring segments in the centrifugal direction. Especially when the retaining bolts are made tubular does there result a light and still durable construction which moreover outstandingly equalizes temperature differences and the associated thermal stresses.

[0006] The retaining bolts can be held in a manner which is simple in terms of production engineering by locking means which act by providing positive-locking support, especially when using interposed springs in the form of short helical compression springs or plate springs temperature-induced material stresses being especially favorably equalized and warping of the brake disc being reliably avoidable even under high temperature loads.

[0007] For internally ventilated brake discs, as a result of the configuration as claimed in the invention, there is a structurally displaced frontal contact area of the ring segments, by which a larger number of cooling channels can be realized, moreover as a result of the tubular configuration of the retaining bolts their likewise forming a cooling channel. In conjunction with an annular ventilation gap which is located between the circumferential sections of the supporting part and the ring segments of the friction ring the cooling of the brake disc is outstanding, with uniform temperature dissipation.

[0008] Especially for steel retaining bolts it can be advantageous to provide them with a coating to prevent corrosion or for optimization of friction. A coating for example of Zr₂O₅ can be applied in a PVD or CVD process especially advantageously. These coatings are especially resistant to temperature and wear.

[0009] In a brake disc with a friction ring with an outside diameter of at least 250 mm, based on the proposed construction there can be at least eight ring segments which can be made as identical parts in a manner favorable to production engineering, which ensure durable construction with reliable stress equalization and which moreover form water drainage grooves as a result of the radial alignment of the frontal contact areas.

[0010] One embodiment of the invention is detailed below with further details.

[0011]FIG. 1 schematically shows a section of the brake disc for a disc brake for motor vehicles with a representation of the retaining bolts which is cutaway in the frontal contact area of the ring segments;

[0012]FIG. 2 shows a section along line II-II of FIG. 1 through the frontal contact area of two ring segments; and

[0013]FIG. 3 shows another section along line III-III of FIG. 1 along one frontal contact area in the middle axis of the retaining bolt.

[0014] The rotationally symmetrical brake disc 10, which is shown only in sections for a disc brake in motor vehicles, is composed essentially of the friction ring 12 of cast steel or ceramic, a cup-shaped supporting part 14 of deep-drawable steel and several tubular retaining bolts 16, likewise of steel, which connect the friction ring 12 to the supporting part 14.

[0015] The friction ring 12 consists of several ring segments 18, in the embodiment for an outside diameter of the brake disc 10 of approximately 300 mm, of twelve ring segments 18.

[0016] Each ring segment 18 on its bilateral frontal contact areas (dividing lines 10 a of FIG. 1) has semicircular recesses 18 a extending in the radial direction which enclose the respective retaining bolts 16 around almost half their outside circumference. At the frontal contact areas 10 a on the two friction sides of the friction disc 12 there remain radially extending gaps s which preclude direct contact of the ring segments 18 among one another and simultaneously form water or brake wear discharge grooves.

[0017] The recesses 18 a are widened in the radially outer section 18 b for holding one short helical compression spring 20 and one ring shoulder-shaped head section 16 a of the retaining bolts 16 respectively.

[0018] Furthermore the retaining bolts 16 are attached by providing positive-locking support in the circumferential sections 14 a of the supporting part 14 radially to the inside by way of locking means. The locking means can be semicircular wedges 22 or elastic steel rings 24 which provide positive-locking support in the corresponding groove-shaped or conical depressions of the retaining bolts 16 and the circumferential sections 14 a, as is apparent on the drawings.

[0019] The connection by the retaining bolts 16 is held radially under pretensioning by the temperature-resistant (and corrosion-resistant) helical compression springs 20 (or by the corresponding plate springs); nevertheless the ring segments 18 with strong temperature changes on the friction ring 12 with minor compression of the helical compression springs 20 can move radially to the outside and thus reduce material stresses. Warping or distortion of the brake disc 10 is thus for the most part avoided.

[0020] In the ring segments 18 (cf. FIG. 2) several radially extending cooling channels 26 with connecting bridges 28 located in between are formed in each. The cooling channels 26 discharge radially to the inside into an annular ventilation gap 30 which is formed between the circumferential sections 14 a of the supporting part 14 or between its outside circumference and the ring segments or their inside periphery.

[0021] Other cooling channels 32 are formed by the tubular retaining bolts 16 which discharge radially to the inside into the cup-shaped supporting part 14 with bridging of the ventilation gap 30.

[0022] To optimize the friction conditions and to prevent corrosion the retaining bolts 16 are provided at least on their contact surfaces to the ring segments 18 with a PVD coating (physical vapor deposition) of Zr₂O₅. 

1. A brake disc for a disc brake, especially in motor vehicles, with a friction ring and a cup-shaped supporting part, the friction ring consisting of several ring segments which adjoin one another in the circumferential direction, characterized in that each of the ring segments (18) in the frontal contact area (10 a) encloses the retaining bolts (16) approximately to the extent of one half in the radial direction, the retaining bolts (16) are mounted in the circumferential sections (14 a) of the supporting part (14), and the retaining bolts (16) provide positive-locking support for the ring segments (18) in the centrifugal direction.
 2. The brake disc as claimed in claim 1, wherein the retaining bolts (16) are held by locking means (22, 24) which act as positive-locking support in the circumferential sections (14 a) of the supporting part (14).
 3. The brake disc as claimed in claim 2, wherein the locking means are semicircular wedges (22) which, by providing positive-locking support, extend into the retaining bolts (16) and into the circumferential sections (14 a).
 4. The brake disc as claimed in one of claims 1 to 3, wherein the retaining bolts (16) lying radially to the outside are provided with head sections (16 a) which provide positive-locking support for the ring segments (18).
 5. The brake disc as claimed in one of claims 1 to 4, wherein the ring segments (18) are held elastically limited by interposition of springs (20) in the centrifugal direction.
 6. The brake disc as claimed in one of claims 1 to 5, wherein the retaining bolts (16) and the corresponding recesses (18 a) are rotationally symmetrical in the frontal contact area (10 a) of the ring segments (18).
 7. The brake disc as claimed in one of claims 1 to 6, wherein the retaining bolts (16) are made tubular.
 8. The brake disc as claimed in one of claims 1 to 7, wherein the retaining bolts (16) are provided with a protective coating.
 9. The brake disc as claimed in claim 8, wherein the coating is a PVD coating of Zr₂O₅ in particular.
 10. The brake disc as claimed in one of claims 1 to 9, wherein the friction ring (12) is made internally ventilated with radially extending cooling channels (26) in the ring segments (18) and wherein between the circumferential sections (14 a) of the supporting part (14) and the ring segments (18) there is an annular ventilation gap (30).
 11. The brake disc as claimed in one of claims 1 to 10, wherein at an outside diameter of the friction ring (12) of at least 250 mm there are at least eight ring segments (18). 